1. Field of the Invention
The present invention relates to a process for premixing-type combustion of liquid fuel in a burner without a premixing section, and to a burner for hot-gas generation, consisting of hollow part-cone bodies making up a complete body, having tangential air inlet slots and feed channels for gaseous and liquid fuels.
2. Discussion of Background
EP-A1-0,210,462 has disclosed a burner which is formed from at least two double-curved hollow part-cone bodies provided with tangential air entry. These bodies are grooved in the direction of flow along diagonals which diverge outwards in the manner of cone lines. One of the curved grooved sides here forms an inner cone with a cone angle increasing in the downstream direction, whereas the other curved grooved side forms an outer cone with a cone angle decreasing in the downstream direction. The inner cones each carry on the end side, over their entire axial extent, a fuel line for feeding the gaseous fuel which flows through several fuel nozzles into the interior of the burner and is mixed there with the combustion air which flows in tangentially. Moreover, the burner has a separate feed for a liquid fuel, so that this represents a dual burner. The injection of the liquid fuel is directed axially upon the outer cones in such a way that a fuel film of varying lengths forms there, depending on the force of the injection. Apart from the natural vaporisation of the liquid fuel due to the radiant heat acting there, considerable mixing is effected by the tangentially introduced combustion air which, due to its spinning motion, unrolls the fuel film layer-wise in the axial direction, so that generation of intensive mixing becomes superfluous. Due to the fact that the momentum of the injection of liquid fuel is adapted to the load of the machine, the mixture is never too lean or too rich.
Two goals can be achieved directly in this way:
The advantages of a premixing burner, namely little NO.sub.x and CO, are obtained.
Good flame stability in a fairly wide operating range is ensured.
Moreover, the constructional design of this burner results in a vortex flow with a low spin in the centre but an excess of axial velocity. Because the spin coefficient then sharply increases in the axial direction and, at the end of the burner, reaches the breakdown value or critical value, the result is a position-stable vortex backflow.
Even though the advantages of the burner described here cannot be denied, it has nevertheless been found that the NO.sub.x and CO emission values, even though they are, as a result of using the burner, already lower than the statutory limits, must be substantially reduced in future. Moreover, it has also been found that coking problems of the outer cone resulting from the combustion of oil cannot be excluded, and the fuel injection is not easy to handle.
Furthermore, the arrangement for the oil injection is relatively complicated constructionally. However, the feeding of the grooved cone sections and their mutual matching are not easy to handle.